Lighting and illumination applications have particular operational requirements in hazardous areas, which are typically industrial and marine environments with harsh climatological conditions and varied hazard factors such as ambient dust, gas and more. Core operational requirements for any equipment, including lighting systems and devices, for use in such areas are codified as IEC and ATEX standards. These standards specify that lighting systems and devices for use in environments with, for instance, explosive characteristics caused by ambient gas or dust, must be designed to prevent any means of ignition arising, to limit the ignition energy of circuits, to prevent an explosive mixture reaching a means of ignition and to prevent any ignition from spreading outside of the apparatus.
In this context, most of the improvements to hazard-proof lighting of the prior art have historically focused upon shock-proofing part or all of the casing of lighting devices, as most such devices still use fluorescent or incandescent light sources, typically light bulbs with a glass casing enclosing either a filament with an inert gas atmosphere, or internally coated with phosphor and enclosing mercury vapor, all of which inherently fragile. Well-known examples of shock-proofing include for instance replacing the plastic casing of lighting devices intended for domestic or office use with a metal casing for industrial use, and covering light source covers made of substantially transparent glass or plastic with a metal mesh.
With the development of high-efficiency and high-power Light-Emitting Diodes (‘LEDs’), it has become possible to use LEDs for lighting and illumination applications. There are numerous technical advantages to the use of LEDs, by comparison to traditional fluorescent and incandescent light sources. LEDs generate electroluminescence from a very low voltage and radiate negligible heat, so are unlikely to damage adjacent objects or fabrics. LEDs have a comparably very low failure rate wherein such failing is by dimming over time rather than an abrupt total failure. LEDs have a significantly longer useful life, frequently estimated at between at least 10,000 hours to multiples of this period, to be contrasted with the useful life of incandescent light bulbs estimated at between 1,000 and 2,000 hours. LEDs are moreover solid-state components, so are difficult to damage with external shock, unlike fluorescent and incandescent bulbs. The adoption of LED light sources has accordingly improved the operational safety of lighting devices and assemblies
However, a shortcoming of LEDs in lighting applications, is that LEDs typically have a very small area, often less than 1 mm2 and cannot provide divergence below a few degrees, whereby single LEDs do not approximate a point source of light giving a spherical light distribution, of the sort provided by traditional bulbs, including the more modern Compact Fluorescent Lamps (‘CFLs’). LEDs are therefore difficult to apply to uses needing a spherical light field, such as lighting and illumination applications in hazardous areas.